He等离子体辅助的纳米钨结构材料的制备

利用He等离子体辅助的方法制备了纳米钨结构材料,采用扫描电子显微镜、轻敲模式原子力显微镜对不同辐照离子剂量和功率变化条件下处理的样品形貌、表面粗糙度等特征进行了分析。结果表明,在放电功率为6 kW,离子能量为220 eV条件下,钨表面先出现纳米孔结构,随着离子辐照剂量的增加,纳米孔径逐渐增加,辐照剂量为1.0×10~(26) ions·m~(-2)时,样品表面呈现密集的无序分布的纳米丝结构层,纳米结构层的厚度也随辐照剂量的增加而增加。高分辨扫描电子显微镜的测试结果表明纳米丝根部与钨基体界面处存在大量的纳米级He泡,由此给出了纳米钨丝是由He泡演化而来的直接证据。     

面向等离子体材料钨中氘/氦滞留行为的研究进展

作为面向等离子体材料,钨(W)在服役的过程中不仅受到等离子体造成的高能热负荷的作用,还受到高束流粒子如氘(D)、氚(T)、氦(He)等的轰击和D-T聚变反应产生的高能中子的影响。W中D、T、He的滞留和起泡,仍是聚变堆装置中有待解决的关键问题之一。综述了D、T和He的滞留行为及其气泡形成与辐照条件之间的关系,简要评述了W的服役性能和强化机理。通过降低W中D/He滞留量、抑制气泡的形成可有效改善W的服役性能。深入研究D/He滞留行为与辐照缺陷之间的相互作用关系,进而构建D/He的宏观热脱附行为与其微观状态之间的对应关系,为寻找合适途径来改善W的服役性能提供理论支撑。     

面向等离子体材料钨中氘/氦滞留行为的研究进展

作为面向等离子体材料,钨(W)在服役的过程中不仅受到等离子体造成的高能热负荷的作用,还受到高束流粒子如氘(D)、氚(T)、氦(He)等的轰击和D-T聚变反应产生的高能中子的影响.W中D、T、He的滞留和起泡,仍是聚变堆装置中有待解决的关键问题之一.综述了D、T和He的滞留行为及其气泡形成与辐照条件之间的关系,简要评述了W的服役性能和强化机理.通过降低W中D/He滞留量、抑制气泡的形成可有效改善W的服役性能.深入研究D/He滞留行为与辐照缺陷之间的相互作用关系,进而构建D/He的宏观热脱附行为与其微观状态之间的对应关系,为寻找合适途径来改善W的服役性能提供理论支撑.     

He~+辐照对非晶碳氢薄膜表面硬度的影响

在室温下,利用等离子体增强的化学气相沉积法(PECVD)在硅衬底上制备了非晶碳氢薄膜。采用100keV,剂量分别为1.0×1015、5.0×1015、5.0×1016和1.0×1017ions/cm2的He离子(He+)对非晶碳氢薄膜进行辐照实验。通过基于原子力显微镜(AFM)的纳米压痕和纳米划痕技术,对He+辐照前后碳氢薄膜的表面硬度进行分析。结果表明,经He+辐照后碳氢薄膜的表面硬度明显增加,并且随着He+辐照剂量增加,碳氢薄膜的表面硬度呈逐渐增加的趋势。傅里叶变换红外光谱(FT-IR)和拉曼光谱分析表明,He+辐照会导致碳氢薄膜中sp2C键含量明显增加,而sp3C键及H原子的含量明显降低,这可能是引起碳氢薄膜硬度变化的主要原因。     

氘和氦离子辐照下CLAM钢的辐照硬化与微结构演变

结合先进电子显微术和纳米压痕分析,对低活化马氏体CLAM钢的辐照行为进行了研究。在室温下对CLAM钢进行了单一注D+、单一注He+以及先注D+后注He+三种方式的离子辐照。纳米压痕硬度结果显示,离子辐照后的CLAM钢均产生了明显的硬化。通过对纳米压痕硬度曲线的拟合,得到各离子辐照后的硬化率。结果表明,注D+的辐照硬化程度最低,而注He+与D+、He+共同辐照的硬化程度均很明显。微观结构分析表明,沿离子注入深度方向,辐照缺陷密度逐渐增加然后减少;在注入深度峰值附近,产生了数密度较多的缺陷。对于单独注入He+离子以及先注D+后注入He+的CLAM钢,都产生了大量细小弥散的He泡,并且由于离子协同效应后者出现深度较浅的泡;单独注入D+的CLAM钢,并没有出现泡。注He+样品中既有位错环也有He泡,硬化效应比只有位错环的注D+样品明显;而先注D+后注He+的样品,由于注D+产生的缺陷在后续注He+时会有一定的回复,硬化效果不是注D+和注He+的简单叠加,体现出协同效应。     

纳米多晶钨膜中He相关缺陷对H滞留的影响*

用磁控溅射方法制备纳米多晶钨膜, 采用X射线衍射(XRD), 扫描电子显微镜(SEM), 弹性反冲探测(ERD)和慢正电子束分析(SPBA)等手段研究了在高能He⁺和H⁺依次对其辐照后He相关缺陷对H滞留的影响。结果表明, 注He⁺钨膜在退火后从β型钨向α型钨转变; 钨膜中的He含量随着退火温度的提高而减少, 在873 K退火加剧钨膜中He原子的释放, 且造成钨膜空位型缺陷的增加和结构无序度的提高; 钨膜中的H滞留总量随着He滞留总量的减少略有下降。     

氩离子减薄对非晶合金晶化过程的影响

在利用电子显微镜观察非晶合金晶化时,常使用离子减薄法制备样品,这实际上是一种重粒子辐照过程。由组成合金元素的高能粒子(MeV 量级)对非晶合金在加热时进     

高能W~(6+)预辐照对钨表面微结构的影响

利用低能H离子对20 Me V W~(6+)预注入和未注入的钨样品进行辐照实验,考察H离子能量(20-520 e V)和辐照温度(673-1073 K)变化对钨表面微结构的影响。采用非破坏性的导电模式原子力显微镜和扫描电镜分析预注入和未注入钨样品的表面形貌和内表面缺陷分布情况。结果表明,辐照后的样品表面出现大量的纳米尺寸凸起,高能W~(6+)预注入的样品表面损伤要小于未注入的钨样品,意味着高能离子预注入会对材料的表面损伤起到抑制作用,但是当辐照温度高于1073 K时,这种抑制作用开始减弱。     

低能大流强氢离子辐照对钨的刻蚀行为

在聚变相关的钨(W)偏滤器辐照下,研究了低能大流强氢(H)离子辐照对多晶钨材料的刻蚀行为。使用扫描电子显微镜(SEM)、导电原子力显微镜和基于SEM的电子背散射衍射等手段研究了大流强(~10²² ions/m²·s)、剂量为1.0×10²⁶ ions/m²、能量为5~200 eV的氢离子辐照对多晶W材料表面刻蚀行为的影响。结果表明,随着H离子辐照能量的增加W的溅射率迅速提高,W表面发生刻蚀后产生条纹状结构,而且同一晶粒上条纹的方向具有一致性,条纹两侧的缺陷分布明显不同,意味着W表面的刻蚀优先沿某一特定晶面方向进行。     

氦离子辐照下钨纳米丝的自保护行为

采用低能量(200 eV)大流强的He⁺辐照多晶钨材料,辐照温度为1023 K和1373 K,辐照剂量为1.0×10²⁵~1.0×10²⁶ ions/m²。用称重、扫描电子显微镜、导电原子力显微镜等手段分析辐照后钨材料的质量损失、表面形貌和内表面缺陷分布,研究了刻蚀速率与表面形貌的关系。结果表明,具有粗糙钨纳米丝表面的钨样品刻蚀速率只有平滑表面的30%。其原因是,在大流强He⁺辐照下钨表面纳米丝的形成阻碍钨原子的溅射。这也意味着,钨纳米丝表面的形成可作为钨材料的自保护结构层,抑制ITER相关辐照下的强刻蚀。     

Hg1-xCdxTe材料AES定量分析中的电子束和离子束效应

在Hg1-xCdxTe材料的AES分析中 ,由于分析电子束辐照作用 ,可诱导表面Hg原子的脱附和热升华 ,导致短时间内样品表面严重失Hg ,使AES定量分析结果产生很大的误差。实验结果表明 ,在超高真空中分析电子束辐照下局部Hg元素的挥发损失以负指数关系进行。通过选择离子束溅射速率大于电子束蒸发速率 ,并在溅射的同时进行俄歇信号收集 ,则可减小或消除分析电子束对元素Hg的蒸发作用 ,获得稳定的俄歇信号。实验结果还指出 ,溅射离子束的参数会影响元素的相对溅射产额 ,具体定量分析时应选择相同的溅射条件     

Electron beam nanoprocessing of a carbon nanotube film using a variable pressure scanning electron microscope

We demonstrate a novel method of processing carbon nanotubes using a variable pressure scanning electron microscope. Lines were processed in a nanotube film by electron beam irradiation in oxygen gas and nitrogen gas. The processing mechanism can be explained in terms of gas ion sputtering and chemical reaction. In this experiment, the narrowest line width of 120 nm was achieved in a nitrogen atmosphere.     

Microstructure analysis of ion beam-induced surface nanostructuring of thin Au film deposited on SiO2 glass

Effects of the irradiation dose on surface nanostructuring accompanied with the dewetting process of Au films deposited on SiO₂ glass were examined using an atomic force microscope and a scanning electron microscope. In addition, the microstructural evolution and the chemical concentration of Au films were investigated using a transmission electron microscope equipped with an energy-dispersive spectrometer. As increasing the Ar ion irradiation dose, the lattice expansion of Au nanoscale islands sustained on the SiO₂ glass was observed and irradiation-induced lattice defects together with irradiation-induced interface ion mixing were accounted for this lattice expansion. Finally a layer of photosensitive Au nanoballs with highly spherical shape embedded in a SiO₂ substrate was obtained after Ar ion irradiation to 10.0 × 10¹⁶/cm² and some of Au nanoballs were found to be single crystals. As the irradiation energy of the Ar ions increased from 100 to 150 keV, the average diameter of the Au nanoballs in the substrate increased and the red shift of the SPR peak was observed. This tendency of the experimental SPR peaks corresponded with that of the theoretically calculated SPR peaks using Mie solution.     

Nickel sputtering by high-energy heavy ions

Recent experimental data on the sputtering of coarse-grained metals by high-energy heavy ions are reviewed. It is pointed out that inelastic energy losses of ions have rather insignificant effect on the sputtering yield of metals. Experimental data on the sputtering of nickel by ⁸⁶Kr⁺ ions are presented. The accumulation of radiation defects in the crystal lattice of nickel in the course of irradiation leads to an increase in the metal sputtering yield from the surface of grains, making it comparable with the sputtering yield from the intergranular region. The results of such experiments are important for development of the heavy ion acceleration facilities and for the high-energy heavy-ion doping of deep layers in semiconductors.     

Effect of 305-MeV krypton ions on the surface of highly oriented pyrolytic graphite

The surface of highly oriented pyrolytic graphite (HOPG) irradiated by 305-MeV krypton ions was studied in a scanning tunneling microscope. It was found that inelastic energy losses of the krypton ions do not significantly affect the sputtering of carbon from the surface of crystalline HOPG grains. Similarly to the case of metals, preferential sputtering takes place in the grain boundaries. The inhomogeneous sputtering of polycrystalline conductors has to be taken into account in interpreting experimental data on the sputtering of such targets by high-energy heavy ions in the range of inelastic energy losses. The results can be also implemented in the technology of ion implantation into deep layers of solids.     

Tin whiskers growth of SnAgIn solder on Kovar substrate with Au/Ni plating

In this research, the interactions of SnInAg solder on Kovar leadframes (Fe29Ni17Co) with Au/Ni UMB was studied, to reveal the whiskers growth mechanism. Samples were prepared by reflow process and aging, with SnInAg solder paste on the substrate. Scanning electron microscope was used to observe the morphology and the cross-sectioned structure of the whiskers. Focused ion-beam was used for the preparation of the transmission electron microscope (TEM) samples, and energy dispersive X-ray and TEM were then used to distinguish the different intermetallic compound (IMC) phases. It was found that, a special solder thickness range would be needed for the growth of whiskers. The root cause of this strip whiskers growth region was studied. It is worthy to mention that, the Sn–Cu reactions, which was reported by many former researches, was not the main source of the compressive stress here. It was found that the Au–Sn reactions, the IMCs transformation during the aging process, and the oxidation layer growth were dominating the whiskers growth. Effects of cracks on the whiskers growth were carefully observed and discussed, and it was found that cracks under a certain width could exempt the breaking of the oxidation layer at the solder surface, thus help the whiskers growth. On the other hand, wide cracks might accommodate the deformation of the solder layer and prohibit the whiskers from being erupted out.     

Polyethylene/palygorskite nanocomposites with macromolecular comb structure via in situ polymerization

Polyethylene/palygorskite nanocomposites with “macromolecular comb” structure were prepared via in situ polymerization. The TiCl₄ catalyst was first loaded on the surface of the nanoscale whiskers of palygorskite. Subsequently the ethylene was introduced into the reaction system, and the polyethylene molecular chain was generated directly at the surface of the palygorskite whiskers. As a result, a polyethylene molecular chain with “macromolecular comb” structure was generated. The product thus obtained was blended with regular polyethylene to make a polymer blend, which was characterized by transmission electron microscope (TEM). Finely dispersed palygorskite whiskers in polyethylene matrix were found, which resulted in the improvement of mechanical strength of the polymer blends. Compared with regular polyethylene, the impact strength and tensile strength of the polymer blend were improved by 63.5% and 21.3% respectively at 25°C, when the palygorskite content of the nanocomposite was 20 wt%.     

氧化还原法制备钨晶须及其生长机理研究

研究了钨晶须的制备工艺,并分析了其生长机理.采用X射线衍射、扫描电镜、能谱分析、透射电镜对制备的钨晶须进行物相、形貌、成分、微观结构的分析和表征.研究表明:钨晶须长度大致在1～10μm,直径在1μm以下,部分达到纳米级;晶须为单晶bcc结构,生长方向为110;钨晶须形成过程为钨粉及其氧化产物与水汽反应生成气相水合物WO2(OH)2,遇氢气还原后形核并沉积,进而定向生长为晶须结构,钨晶须的生成遵循VS机理.     

Low energy Ar+ ion beam irradiation effects on Si ripple pattern

Etching of surfaces by ion beam sputtering is widely used to pattern surfaces. Recent studies using the high-spatial-resolution capability of the scanning tunneling microscope, atomic force microscope and SEM (Scanning Electron Microscopy) disclose in fact that ion bombardment creates repetitive structures at micro-nanometre scale, waves (ripples), checkerboards or pyramids. The phenomenon is related to the interaction between ion erosion and diffusion of adatoms (vacancies), which causes surface re-organization. In this paper we investigated the ripple pattern formation on Si substrates by low energy Ar+ ion bombardment and the dose effect on ripple size. We also briefly discussed the irradiation effects (at normal incidence) on ripple pattern for different irradiation time. Finally, based on Bradley and Harper (BH) theory we proposed a model to understand the mechanism of ripple pattern change due to Ar+ ion beam irradiation.     

Microtopography of surfaces eroded by ion-bombardment

Conical protrusions have been observed in the scanning electron microscope on surfaces that have been eroded by sputtering under 5 to 8 keV A⁺ ion bombardment. It is shown why these have a half-angle corresponding to the principal peak in the graph of sputtering rate versus angle of ion incidence. These lead to some general conclusions on the microtopography ofion-eroded surfaces.